Although there are many challenges in conducting a comprehensive formal CRA, industrial hygienists can take some steps to move toward CRA implementation and align with current occupational risk assessment practice (see Figure 1). Ways to incorporate CRA perspectives include:

MOA is the use of toxicology and physiology to identify the way a stressor affects human health. Using this concept, IHs can survey the workplace to identify potential combined stressor exposures that might be particularly problematic. Dusting off the toxicology textbook will go a long way toward developing such a hazard characterization. For example, if screening a list of materials present in a work task during the job hazard analysis (JHA) shows significant potential exposure to nervous system toxicants such as solvents, then extra scrutiny to identify physiological stressors like fatigue would be warranted. If exposures involve cardiotoxic materials, then activities that require extensive cardiovascular stress would merit review. It’s important to note that in each of these cases the individual stressors would be managed below their respective limits per traditional industrial hygiene practice, but the goal is to go beyond that traditional approach to systematically consider and document potential interactions that are unaccounted for.

Because the potential for interactions is complex, and in many workplaces the number of potential hazards (stressors) is large, a systematic tool to supplement the traditional JHA would be very helpful. Such a tool was proposed in a presentation at the 2014 annual meeting of the . The tool lists identified stressors, their routes of exposure, mode of toxic action, and potential for interactions. The tool can vary in complexity and level of documentation. The primary goal is to ensure that combinations of stressors are specifically evaluated as part of the JHA process.

To date, the primary quantitative risk characterization tool used by the IH is the occupational exposure limit. In most cases, the OEL does not consider unique CRA needs for the scenario for which it is applied. Instead, OELs are intended to be generally applicable limits that include an in-depth review of the toxicity profile for the chemical or hazard irrespective of site-specific exposure scenarios. Thus, the OEL can be viewed as a starting point that can be adjusted, based on the IH’s professional judgment, to take into consideration other factors in the environmental or occupational scenario.

One mechanism for adjusting the OEL is the establishment of a JHA or site-specific action level (AL). The IH would interpret the OEL based on site-specific factors so that the AL is set below the OEL. This could be accomplished through two approaches. The first approach would require reducing the AL based on non-work-related exposures common in the work force that might increase susceptibility to the toxicity of the agent under concern. The second approach would account for potential cumulative risks due to workplace exposure or interactions. In both approaches, the IH would need to make a site- or scenario-specific adjustment to the uncertainty factor for variability in worker susceptibility that is already embedded in the derivation of most OELs.

Non-work-related factors are not directly under the purview of the IH, and legal barriers divide work- and non-work settings. But opportunities exist for IHs to affect cumulative risks for mixed domains of exposure (work, consumer, and environment, for example). Ensuring close communication with occupational medical care providers is one way IHs can overcome these barriers. While IHs do not direct risk mitigation outside the workplace, they can educate and inform the healthcare community, who can reinforce these messages when they interact with workers. CRAs differ from traditional risk assessments with respect to exposure potential (single stressor vs. multiple stressors), stressor type (chemical only vs. chemical and non-chemical), health endpoint (single vs. multiple; additive vs. interactive effects), and metrics by which to assess health risk (traditional vs. non-traditional metrics of exposure and effects). With these differences in mind, consider the following scenarios:

You have been asked to conduct an industrial hygiene assessment of a new production facility. The employer wants to ensure the health and safety of the operations before employees start working at the facility.

You have been asked to conduct an industrial hygiene assessment of an existing production facility where employees have complained of a range of health effects (headache, dizziness, nausea, eye and throat irritation, dermatitis).

How would you go about completing this assignment? What sources (stressors) do you consider? How do you measure or characterize exposures or co-exposures? What types of health effects do you consider? Where do you get your information or data? How do you determine whether there is a risk? Do you consider non-additivity of risks? What type of controls do you recommend?

Although a traditional risk assessment could answer these questions, a CRA approach would provide a much fuller characterization of the different sources of exposures and health effects, which is useful for implementing risk management controls. Assessing cumulative risk is a complex process riddled with uncertainties and technical challenges. Implementing CRAs that fully address these issues and successfully integrate occupational and non-occupational stressors will require new frameworks and tools. Advancing CRA and applying these approaches in occupational settings largely depends on the involvement of the industrial hygiene community. The above outlines eight activities that IHs could champion to help advance the development and use of CRA in occupational settings. CRA approaches hold great potential, but without our participation they will remain limited and not suited for characterizing complex workplace exposures.